"Are you sure, Mr Pistorius, that Reeva did not scream after you fired the first shot?" asked Nel.

The athlete, who earlier said he was tired and struggling under the relentless interrogation, leaned back in the witness box and remained silent. The wood-lined courtroom in South Africa was hushed and expectant on Friday. Was Pistorius thinking through an answer, or was he on the verge of an emotional outburst, or was he reflecting on his predicament and Reeva Steenkamp, the girlfriend he killed in his home last year?

After a tense pause, the Olympic athlete said he wished Steenkamp had let him know she was in the toilet cubicle where he shot her — by mistake, according to his account. He said she did not scream, but also that his ears were ringing with the gunshot and he would not have heard screams.

Pistorius often seemed worn down as the caustic prosecutor picked holes in parts of his story. The dramatic cross-examination has drawn attention to Nel, a prominent state prosecutor dubbed "pitbull" in local media and on social networks for his combative, often effective style.

One of the highlights of his career came in 2010 when he secured the conviction on corruption charges of Jackie Selebi, a former national police commissioner and ex-president of Interpol — Nel got an international prosecutors' award for his efforts in that case.

Now Nel's international profile is ascending further after three days of challenging and even ridiculing the claim by Pistorius, 27, that he accidentally killed Steenkamp, 29, by firing through a closed toilet door, mistaking her for an intruder in his house before dawn on Feb. 14, 2013. The prosecution says the double-amputee runner is lying, and that he killed his girlfriend after an argument during which she fled into the toilet cubicle to seek refuge. Nel will continue questioning Pistorius on Monday.

A radio station made a parody rap song about defense lawyer Barry Roux, and now Nel has one too ("They call me Gerrie Nel/And I am mad as hell.") In The Times, a South African newspaper, cartoonist Zapiro depicted Nel as a bullet, his head on the tip, speeding toward an alarmed Pistorius.

He has a gentler side, according to Rapport newspaper. It reported that in his personal time, Nel teaches young children how to wrestle and that he is patient and never loses his temper with his students.

Pistorius' murder trial is being broadcast on television. While Pistorius is not shown on the screen during his testimony, viewers have watched Nel browbeat the once globally admired figure who reached a pinnacle when he ran in the London Olympics in 2012. Pistorius, who has been free on bail for the last year, could be jailed for 25 years to life if convicted of premeditated murder and also faces three separate, gun-related charges.

"You will blame anybody but yourself," Nel told Pistorius last week in an attack on the character of the athlete. It was an attempt to shred the defense's presentation of its client as humble, responsible and loving toward the woman he killed. At one point, Nel laughed derisively at one of a number of answers from Pistorius that he described as evasive or contradictory, or downright false, prompting Judge Thokozile Masipa to reprimand the prosecutor for the outburst.

On another occasion, Masipa cautioned Nel to "mind your language" for accusing the athlete of lying.

In 2008, Nel was arrested in what his backers said was an attempt to interfere with the case against Selebi, the former police chief, but he was soon cleared. Nel was also head of the regional branch of the Scorpions, a crime-fighting unit that was later disbanded in a decision that raised concern about the independence of law enforcement from politics. He was a prosecutor in a case leading to the convictions of two men for the 1993 killing of Chris Hani, an anti-apartheid leader whose death stirred fears of racial violence as South Africa transitioned from white rule to an all-race democracy.

Surrounded by security, Pistorius daily leaves the Pretoria court to fend his way through a crush of press and bystanders. On a recent afternoon, Nel left the court quietly, unassuming in a dark suit and open-necked shirt. Despite his newfound celebrity status, he walked across the street, almost unnoticed.